Blacks are at increased risk for noninsulin dependent diabetes mellitus (NIDDM), obesity, cardiovascular disease and hypertension. A common pathogenetic link among these entities could be hyperinsulinemia/insulin resistance. The goal of this project is to test the hypothesis that black children, compared with their white counterparts, have an inherent reduction in insulin action. Specific aims are 1a) To determine whether or not black children are more insulin resistant than white children independent of family history of NIDDM. 1b) To quantitate the earliest impairments in glucose and fat metabolism by a cross-sectional study of prepubertal black vs white children, and pubertal black vs white adolescents. 1c) To evaluate the impact of physical activity/fitness on insulin sensitivity in black vs white children. 2a) To determine if for the same degree of obesity (total and abdominal) black children are more insulin resistant than white children. 2b) To assess if during an intravenous intralipid challenge, black adolescents are more likely than whites to store rather than combust the fat load.